Ferry From Zhongshan to HKIA to pick up somebody

I will be in Zhongshan and I am planning to take a ferry from there to HK Airport.

I need to go to the airport to pick up my wife that will be arriving there in the afternoon of the same day. We will spend a few days in HK for holidays.

My doubt is if I will be allowed to take a ferry to the airport but not board any flight the same day.

I am questioning this once, last year, I tried to take a ferry from Shekou to the airport but they told me that I could go to the airport only if I had a flight booked for the same day.

Could you please clarify this to me.

Vladimir de Souza